China ordered the nation's commercial pilots to learn to "land blind" in smoggy conditions to help alleviate chronic flight delays.

Pilots flying to Beijing's international airport from the nation's 10 busiest airports must be qualified to land when visibility falls below 400 metres, starting from January 1, the official China Daily said, citing unidentified people at the Civil Aviation Administration of China.

The new requirement, translated as "level two blind landing," uses radio beam transmitters to guide planes when pilots have difficulty seeing, according to the Xinhua News Agency.

Smog is hurting efforts to improve on-time performance in China, where about one in four flights is delayed because of airspace congestion.

Haze that engulfed Shanghai this month sent air pollution to record highs, causing the cancellation of more than 200 flights in a 24-hour period.

Beijing and Shanghai had one-time departure rates of 38 per cent and 39 per cent in October respectively, the worst among 35 major international airports, according to Portland, Oregon-based FlightStats.

Shanghai-based China Eastern Airlines, the nation's second-biggest carrier, has 1400 pilots that are qualified to meet the new requirements, the company said.

Spring Airlines, China's largest outside government control, said it's training pilots to land in smog. The smog in Shanghai this month affected the company's operation, it said.

Hong Kong-based Cathay Pacific Airways said the new rule would only apply to mainland Chinese carriersl.

About 40 per cent of flight delays in China are caused by air operators, 27 per cent by flow control, while the rest is due to other factors such as bad weather, Li Jiaxiang, head of the civil air regulator, said last year.

In January, Beijing suffered its worst bout of air pollution with PM2.5 readings hitting at least 886. Shanghai's air pollution index surged to a record 482 on December 6 into the "severe" level, the highest of a six-tier rating system.

The haze also caused traffic congestion the nation's commercial hub as the government took emergency steps such as ordering cars off the road and factories to cut production.

The average concentration of PM2.5, particulate matter that is smaller than 2.5 microns in diameter, was 76 micrograms per cubic meter in 74 cities in the first six months, according to the environmental protection ministry. That's nearly three times the level of daily exposure recommended by the World Health Organization.

Premier Li Keqiang pledged in March to clean up pollution including cutting coal consumption, shutting steel plants and controlling the number of cars.